Predetermined torque release wrench



Nov. 8, 1960 R. H. SKIDMORE PREDETERMINED TORQUE RELEASE WRENCH Filed June 17, 1959 4 fzm INVENTOR. 4 RICHARD H. .SK/OMOIQF United States Patent '0 i PREDETERMINED TORQUE RELEASE WRENCH Richard H. Skidmore, Lyndhurst, Ohio, assignor to Skidmore-Hungerford Industries, Inc., Bedford Heights, Ohio, a corporation of Ohio Filed June 17, 1959, Ser. No. 820,977

6 Claims. (Cl. 8152.4)

This invention relates to improvements in a wrench and more particularly to an adjustable torque wrench.

One of the objects of the present invention is to pro vide a torque wrench having a roller type follower engaging its camming surface with a rolling contact to minimize friction.

A further object of the present invention is to provide a torque wrench having a pin-type roller bearing rotatably mounting this roller follower.

A further object of the present invention is to provide a torque wrench having flat camming surface portions engaging a follower in both initial and tripped positions.

A further object of the present invention is to provide a torque wrench providing an audible signal during movement between initial and tripped positions in response to application of a predetermined torque.

A further object of the present invention is to provide a torque wrench automatically movable in the reverse direction back from the tripped position to the initial position upon release of the applied torque. 1

A further object of the present invention is to provide a torque wrench characterized by its accurate adjustment, compact size, light weight, economical construction, simplicity of design, rugged construction, ease of assembly of its component parts, and ease of use.

Other features of this invention reside in the arrangement and design of the parts for carrying out their appropriate functions.

Other objects and advantages of this invention will be apparent from the accompanying drawings and description and the essential features will be set forth in the appended claims.

In the drawings,

Fig. 1 is a side elevational view of the adjustable torque wrench disclosed herein;

Fig. 2 is a longitudinal section taken along the line 22 in Fig. 1;

Fig. 3 is an enlargement of a portion of Fig. 2 of the roller follower and its mounting member; while Fig. 4 is an enlarged longitudinal sectional view taken generally along the line 44 in Fig. 2 with the relative positions of roller and camming surface shown with respect to the other parts of the wrench in solid line for initial position and in dot-dash line for actuated position.

Before the torque wrench here illustrated is specifically described, it is to be understood that the invention here involved is not limited to the structural details or arrangement of parts here shown since a torque wrench embodying the present invention may take various forms. It also is to be understood that the phraseology or termi nology herein employed is for purposes of description and not of limitation since the scope of the present invention is denoted by the appended claims.

Those familiar with this art will recognize that my invention may be applied in many ways, but it has been chosen to illustrate the same as an adjustable torque wrench.

Cylindrical housing provides the casing for the 2,959,078 Patented Nov. 8, 1960 ice wrench with this housing including an upper part 10a and lower part 10b with each part being tubular. These parts are illustrated in the drawings as being telescopical ly assembled and have coaxial, cylindrical bores 10a-1 and 1011-1.

These housing parts 10a and 10b are secured in assembled relationship in any suitable manner, such as by a drive or force fit, welded joint, screw threads, etc.

Upper part 10a has a work-engaging member or lever 12 connected thereto by pivot 13. The upper end of lever 12 is arranged to engage a bolt to be tightened. Here the end is bent laterally at degrees and has a square projecting portion or work-engaging portion 12a with conventional spring pressed ball 14 in a hole thereof adapted to grip a square, female hole in a socket or ratchet having on its opposite end a coaxial male or female portion adapted to engage in a recessed bolt head or over a conventional bolt head or nut. Tang 12b of lever 12 on the opposite side of pivot 13 from portion 12a may have any suitable follower thereon but preferably a roller-type follower 16 rotatably mounted by a needle-type roller bearing 18 on an axle 20 secured at opposite ends in coaxial holes in tang 12b.

Pivot 13 operatively connects member 12 to housing 10 for relative movement of follower 16 and housing 10 through an arcuate path 28 in Fig. 4 about pivot 13. Pivot 13 includes screws 15 screwed into coaxial tapped holes 12d in member 12 and having their heads rotatably mounted in coaxial holes 10a-2 in housing part 10a.

Lower part 10b has plug 21 fixed therein in any suitable manner, such as by a force fit, welding, or screw threads, with this plug having a screw threaded bore 21a within which an Allen head screw 22 is screwed. The upper end of screw 22 presses against the lower end of member 23 having a cylindrical surface 23a telescopical ly movable in bore 10b-1; and carrying rod 25 coaxial with cylindrical surface 23a with rod 25 having a knurled surface 25a held by a press fit in bore 23b of member 23. Hence, rotation of screw 22 is adapted to move member 23 telescopically and axially within bore 10b-1. Block 24 has a cylindrical periphery 24c axially movable in bore 10b-1 of housing 10 and a camming surface 24b. A suitable resilient means, such as compression spring 22, is laterally centered'by bore 10'b-1 and biases block 24 in upward direction 26 within housing 10.

The mode of operation should now be generally apparent. When the socket or ratchet on square projection portion 12a is engaged with a nut or bolt head, housing 10 is held by the hand portion 10c to turn the wrench and the nut or bolt head in the tightening or clockwise direction 31 in Fig. 1 about axis 12 by applying torque by the troque wrench to the nut or bolt. As a predetermined'work-engaging force or torque is applied bythe wrench to the nut or bolt through surface 24b and roller 16, relative movement takes place between roller follower 16 and the assembly including block 24 and housing 10 from initial position 32 in Fig. 4 to tripped position 30 with Fig. 4 showing the relative position of roller 16 and surface 24b with respect to the rest of the wrench in these two respective positions in solid line and dot-dash lines. Although roller follower 16 is shown in two different positions for simplicity of illustration, it should be readily understood that the actual movement takes place by having housing 10 moved with respect to roller follower 16 between these positions since the increased torque advances housing 10 in direction 31 with respect to member 12 held against further movement by the nut or bolt being tightened. However, Fig. 4 still shows the relative postion between roller 16 and cam surface 24b and the rest of the parts in the wrench with the tripped or one position 30 shown in dot-dash :used "satisfactorily; .angle 34 maybe degrees.

line position and the other or initial position 32 shown in solid line. During movement between these positions, the different portions of housing each move through one ofa seriesofar cu-ate paths 28 centered at pivot 13 and extending generally transverse to the direction 26 in which block 24 is biased by spring '22. Hence, when this predetermined torque is applied, .this tendency to move from initial position 32 to trip position 30 is resisted by the compressive force of spring 22 pushing block 24 in direction 26, but this predetermined torque causes roller follower 16 to push cam surface 241; in the downward direction opposite the direction 26 so that the parts canmove to the tripped position 30 with roller 16 rolling uphill on blocklsurface 24b during this movement betweenjthese vpositions. 2 Cam. surface -24b.includes sharp shoulder 2412-1 at the intersection or two angularly related, flat portions mined torque desired because the force required for moving the parts between initial position 32 and tripped position 30 may be adjusted. "First, during assembly, the relative axial location of housing parts 10a and 10b in final assembly will determine the preloading on spring 22 so as to establish the range of adiustment. Second, within this range, the torque wrench may be adjusted by rotating screw 22 in either of two opposite directions so as to move member 23 in direction 26 or in the opposite axial direction so as to increase or decrease the axial loading on spring 22. Indicator mark 23d on block member 23 is adapted to be read in Fig. 1 through open- 7 ing 10b-3 of part 10b and. may be calibrated with respect to indicator marks l0b-2 on housing part 101; as a visual 24b-2 .and24b-3respectively engaged'byroller 16 to deindication of the relative axial position of member 23 with respect to housing 10, the axial force exerted on block 24 by spring 22 in direction 26, and the predetermined torque required to move the parts from position 32 to position30.

I. believe one of the advantages of my torque wrench over those of the prior art is illustrated when one com: pares the torque developed with progressive increments of movement of'the handle or housing 10. With the first movement of the parts from the condition shown shoulder 2415-1, and are inclined in the same direction with respect to path 28, namely upwardly and toward the right in Fig. 4. One portion 2411-2 extends generally parallel to path 28 by being inclined by angle 34 approximately 6 to 8 degreeswith respect to plane 35, and is located above for on the follower side of path 28 as is apparent by comparing angle 34 with path 28 in Fig. 4. Other portion 2412-3 is located on the opposite side of or belowpath 28 and is inclined at an angle 37 of Proferably approximately not under 25 degrees and not over 35 degrees with respect to plane 35. It shoiildbe noted that portion 245-2 is angularly inclined less steeply with respect to path 28 and plane 35 than portion 24b-3; the surface of roller 16 engages surface portion 2417-2 in position and the surface of this roller engages surface portion 2411-3 in position 32 with the engagement in this last position preferably being held to inch but no greater than inch from shoulder 24b-1, as shown by dimension 38. These aforementioned preferred angles and dimension are for a torque Wrench radius swingdimensionR in'Fig. 1 of about three inches,

but will also be satisfactory for a dime'nsion'R of about 12 .inches.

As thepredetermined torque is applied and the parts move.- from initial position 32 to" tripped position 30, rollerlo travels over, shoulder 2412-1 andengages' housing 10a so as .to emit .an audible click to indicatethat the boltlorinutnhas been tightened wtili the predetermined torque desiredQ l 4 Upon reiea'serof this torque orv force, spring22 will cause the parts to'return to the initial'position 32 by causing roller 16 to roll downhill on cam surface 24b.

However, vsatisfactory results have been obtained with angle 34 at 7 degrees with dimension R of three or twelve inches.

7 A minimum of sliding friction exists in this torque wrench becauseroller 16,'rotatable with minimum friction by needle bearing .18, has rolling contact on flat portions 24b-2 and 2417-3. This construction requires less particularity in design and manufacture andis easier to. operate than a. ball, other type follower, or other type cammingsui faces l heat ra str t h i adju b f r ar. p e

When dimension R is 12 inches,

in Fig. 4, the roller 16 starts to climb the cam surface 2411-3 with the result that there is a sudden increase of torque from zero to maximum, and then just as the roller passesjthe sharp shoulder 24b-1, the torque falls off suddenly and sharply to a fairly constant level indicated by the effect of the cam surface 24b-2 on the roller 16 tending to move it clockwise or in the return direction as shown in Fig. 4. This sudden release of torque as the roller 16 passes the sharp shoulder 2411-1 causes the hand of the operator to suddenly carry the parts to the dot-dash position indicated at 30 in Fig. 4 with a loud snap as the roller .16 strikes the housing partltla'. To the best of my knowledge and belief, no prior art device does this but, instead, as the device passes the peak of the jtorque developed, the torque falls oif more gradually than in my device so that there is not "such a clear indication that the desired limit has been reached.

The upper end of rod 25 in Fig. 2 is adapted to axially engage against the lower end of block 24 during axial relative approach movement of blocks 23 and 24 to prevent spring 22 from going into'solid height beyond the adjustment of the wrench.

Various changes in details and arrangement of parts can be made by one skilled in the art'without departing from either the spirit of this invention or the scope of the appended claims.

What is claimed is: v p

'In a predetermined torque release wrench of the class having a housing, a block movable in said housing, resilient means biasing said block to move in said housing in. one direction extending perpendicular to a reference plane; a work-engaging member having a follower engaging a surface on said block for restricting block movement in said one direction, and meansoperatively connecting said member to said housing for relative move ment of said follower and housing through a path generally transverse to said one direction from one posi-' tion to another position, said block surface having two flat portions respectively engaged by said follower to.

opposite sideof said path.

3. In a predetermined torque release wrench of the class having a housing, a block movable in said housing, resilient means biasing said block to move in one direction in said housing, a work-engaging member having a follower engaging a surface on said block for restricting block movement in said one direction, and means operatively connecting said member to said housing for relative movement of said follower and housing through a path generally transverse to said one direction from one position to another position, said block surface having two flat portions respectively engaged by said follower to determine said positions, said block surface having said two portions angularly related and connected by a shoulder so that movement of said member between said positions carries said follower over said shoulder.

4. In a predetermined torque release wrench, as set forth in claim 3, with one of said portions being angularly inclined less steeply with respect to said path than the other of said portions, said follower engaging said other portion in one of said positions a distance no greater than ,4 inch from said shoulder.

5. In a predetermined torque release wrench of the class having a housing, a block movable in said housing, resilient means biasing said block to move in one direction in said housing, a work-engaging member having a follower engaging a surface on said block for restricting block movement in said one direction, and means operatively connecting said member to said housing for relative movement of said follower and housing through a path generally transverse to said one direction from one position to another position, said follower being a roller rotatably mounted by a needle-type roller bearing on said member with said roller being adapted to roll on said block surface during movement between said positions.

6. In a predetermined torque release wrench, a housing, a block movable in said housing, resilient means biasing said block to move in one direction in said housing, a work-engaging member having a follower engaging a surface on said block for restricting block movement in said one direction, and means operatively connecting said member to said housing for relative movement of said follower and housing through a path generally transverse to said one direction from one position to another position, said block surface having two flat portions respectively engaged by said follower to determine said positions with portions of said housing, said block portions meeting at a common shoulder with both block portions being inclined in the same direction with respect to said path with one block portion located on the follower side of said path and the other block portion located on the opposite side of said path, said follower engaging said one block portion in said one position, said block portions being inclined with respect to said path so that a predetermined work-engaging force applied through said surface and follower will cause movement from said other to said one position against the bias of said resilient means while emitting an audible click by said follower striking one of said portions in said one position and so that release of said force will cause movement back from said one to other position by the bias of said resilient means urging said block in said one direction toward said follower.

References Cited in the file of this patent UNITED STATES PATENTS 2,365,486 Morris Dec. 19, 1944 2,731,865 Woods Ian. 24, 1956 2,732,747 Livermont Jan. 31, 1956 2,743,638 Woods May 1, 1956 2,887,919 Aiiala May 26, 1959 2,887,921 Livermont May 26, 1959 2,899,854 Livermont Aug. 18, 1959 FOREIGN PATENTS 1,063,803 France Dec. 23, 1953 

